Steam generator having a flue and an access shaft



June 10, 1969 UTwlNOFF 3,448,726

STEAM GENERATOR HAVING A FLUE AND AN ACCESS SHAFT Filed Dec. 18, 1967 Sheet of 2 5 III 13 12 4 ll ll" 1 (11) i Inventor:

RICHARD L TWINQFF' June 10, 1969 R. LlTWlNOFF STEAM GENERATOR HAVING A FLUE AND AN ACCESS SHAFT Filed Dec. 18. 1967 Sheet & 01 2 Fig.2

- Inventor.-

RICHIQPD L ITW/NOFF United States Patent 18,527 Int. Cl. F22b 37/10, 15/00, 25/00 US. Cl. 122235 8 Claims ABSTRACT OF THE DISCLOSURE The access shaft is disposed within the walls of the flue and is arranged in parallel relation to the flue walls in order to avoid the need of any ingress apertures in the side walls of the flue. The shaft has openings adjacent the spaces between the nests of tubes to provide entry from the shaft into these spaces for inspection or repair of the nests of tubes.

This invention relates to a steam generator having a flue and an access shaft. More particularly, this invention relates to a steam generator having a flue and an internal access shaft.

Heretofore, steam generators which have been constructed with a flue, the walls of which are covered by tubes, and spaced nests of tubes withinthe flue have had accessible spaces between adjacent nests of tubes. In order to enable inspection or repair of the nests of tubes from these accessible spaces, lockable ingress apertures have been provided in the side walls of the flue at thelevels of each accessible space. However, this construction has been very expensive since the tubes covering the wall have necessarily required special shaping in the vicinity of the ingress apertures. Further, since the ingress apertures have required doors for closing off the apertures, such doors have frequently been a source of danger as the seals between the apertures and doors can easily become leakage points.

Accordingly, it is an object of the invention to permit access to the nests of tubes within a steam generator from within the steam generator.

It is another object of the invention to avoid the need for ingress openings in the side wallsof 'a flue of a steam generator.

It is another object of the invention to prevent leakage from a steam generator through the side walls of a flue therein.

Briefly, the invention provides a steam generator having a flue containing spaced nests of tubes therein with an access shaft parallel to and within the tube covered boundary walls of the flue. The access shaft is sized so as to permit a person to pass through into the nests of tubes. In addition, the access shaft is provided with an aperture at the level of each accessible space between the nests of tubes to permit entry into these accessible spaces. The access shaft is formed so that penetration of the flue gas through the tubes about the flue side walls is avoided.

In one embodiment, the access shaft is formed with a continuous sheet metal pipe. In this embodiment, the pipe is apertured at the levels of the accessible spaces between the nests of tubes and is provided with flaps at these levels to close off the apertures.

In another embodiment, the access shaft is formed of spaced individual sections of sheet metal pipe. Each section of pipe extends over the height of one nest of tubes and includes a flap for closing off the shaft. In this embodiment, the aperture leading to the accessible space can be made very large within the shaft so as not only to increase the freedom of movement permited the person en- 3,448,726 Patented June 10, 1969 tering the accessible spaces but also to reduce the amount of material required for the shaft. In addition, each section of pipe is suspended from one of the tube lined walls of the flue so that the wall of the flue constitutes a wall of the access shaft. This wall of the flue is thus available for inspection as well as being subject to being heated by the flue gas.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken inconjunction with the accompanying drawings in which:

FIG. 1 illustrates a vertical section through a powertype steam generator of the invention;

FIG. 2 illustrates a fragmentary perspective view of a modified access shaft of the invention in place in a steam generator of the above type; and

FIG. 3 illustrates a fragmentary sectional view of a section of the access shaft of FIG. 2. suspended from the tube lined wall of the flue.

Referring to FIG. 1, the power-type steam generator 2 is suspended from a supporting frame 1. The steam gener-ator 2 has a gas tight tubular wall 3 which encloses a combustion chamber 6 and a gas flue 30 above the combustion chamber. The upper end of the gas flue 30 merges into a cover 4 adjacent to a chimney 5 for expelling the combustion gas as is known. In addition, a heating surface 7 constructed in the form of partitions is disposed in the upper end of the combustion chamber 6 while heating surfaces 8, 9, 10, 11 constructed in the form of nests of tubes are disposed in the subsequent flue 30. An accessible space 7', 8, 9, 10', 11' is provided above each of the heating surfaces so as to permit a person to move about.

An access shaft 12 is positioned within the wall 3 in the flue 30 and in parallel relation to the wall 3. The shaft 12 is formed of a continuous sheet metal pipe of rectangular cross-section and penetrates through the cover 4 down into the nests of tubes 8, '9, 10, 11 to permit passage of a person. The top end of the shaft 12 which provides 'access to the shaft 12 is closed by a cover 13 while a ladder 19 is fixed to an interior wall of the shaft 12 for permitting a person to climb down into the nests of tubes. The wall of the shaft :12 adjacent .the nests of tubes is provided with apertures at the level of each accessible space 8',-9', 10', 11 as well as flaps 14, 15, 16, 17 for closing off each aperture. When in a vertical position as indicated by the solid lines, the flaps close off the apertures while when in a generally horizontal position as indicated by the dashed lines, the flaps serve as floors. Additionally the flaps can be made to assume a third position, that is, the flaps can be allowed to hang downwardly in the shaft.

Another flap 18 is secured to the 'bottom end of the access shaft 12 to close off the shaft bottom. The flap 18 can be moved into a depending position as shown in dashed lines to provide access to the space 7 above the lower heating surface 7.

The flaps 14 to 18 are each provided with a suitable securing means (not shown) to permit securement in the respective horizontal and vertical positions described above.

In order to inspect or repair the nests of tubes 8, 9, 10, 11, the cover 13 is opened and the person gaining access to the shaft "12 moves down the ladder 19. The flap 17 is then brought into the horizontal position shown in dashed lines or into the downwardly hanging position. and the person moves into the space 11'. Upon completion of the inspection or repair, the person moves back into the shaft 12 and either closes the apertures with the flap 17 or moves the flap 17 downwardly to allow entry into the lower sections of the shaft 12. This procedure is followed to gain access to the other spaces 10', 9', 8 between the nests of tubes. A similar procedure is 'followed to gain access to the lower space 7.

It is noted that during operation of the steam generator that the flaps 14 to 18 are in the positions shown in solid lines in order to prevent a flow of flue gas through the access shaft 12 past the nests of tubes 8 to 11.

Referring to FIG. 2, the access shaft 12 can otherwise be made of spaced individual sections of sheet metal pipe 23, 24 of balcony-like box shape one above the other which are suspended from the tube wall 3. The adjacent side of the tube wall 3 thus serves as the remaining fourth wall of the access shaft 12. In each case, the height of each section extends over the height of an adjacent nest of tubes 28, 29 constructed as above. Also, the rungs of the ladder 19 are secured to the side walls of the sections 23, 24 while extending both above and below each section such as section 23 or only above each section such as section 24 so as to provide a continuous ladder.

Referring to FIG. 3, the shaft sections 23, 24 are formed with hooks 27 which are cut into the side walls and which are engaged over lugs 26 welded to the side of the tube wall 3. Additionally, if necessary to secure the shaft sections 23, 24 in the suspended state, a spot weld is made between each lug and adjacent hook.

Referring again to FIG. 2, each section 23, 24 is provided with a flap 25 which, in the position shown, closes the shaft and simultaneously serves as a floor which a person can enter into the space above the nests of tubes 28, 2.9. It is noted that the nests of tubes are carried on supporting tubes 31, 32 which are disposed in groups in a staggered arrangement with respect to each other. Thus, a person is able to pass easily from the shaft 12 into the space above a nest of tubes.

In order to pass over the nest of tubes 29 to the space above the nest of tubes 28, the flap 25 in the section 24 is raised into the dashed line position so that one can climb down into the section 23. From here, the persons can move into the space above the nest of tubes 28.

It is noted that this access shaft is accessible from above in a suitable manner (not shown), such, for example, as described above, with a closeable aperture provided in the flue cover. Further, instead of installing the shaft sections in alignment, the shaft sections can be disposed in a staggered arrangement.

The access shaft of the invention is not limited to steam generators of the tower-type but also can be incorporated in steam generators having a flue disposed in parallel relation alongside a combustion chamber. Further, the access shaft can also be used in a horizontally disposed flue.

While the above access shafts have been described as being entered from above through the flue cover, entry can also be obtained from the bottom, for example, through the ash hopper or through a burner nozzle. Also, instead of disposing the access shaft along the side Wall of the flue, the access shaft can be disposed centrally in the flue. This has the advantage that the walls of the shaft are subjected to an even heat loading over their entire surface.

The invention thus provides a steam generator with an access shaft for entering into the spaces between the heating surfaces which is void of any lateral ingress apertures in the exterior walls of the flue. Therefore, the need for special tube constructions which would otherwise have to be provided in the vicinity of the ingress apertures is not required. Hence, the tube lining of the flue walls can be economically manufactured. This is especially advantageous where the tubes of the tube lining are welded together in a gas tight manner. A further advantage of the invention resides in the fact that leaks can no longer occur in the flue Walls. Also, because special shaping of the tubes is avoided, the difficulties arising from additional stressing of the tubes clue to differing elastic behavior of the tubes are also avoided.

What is claimed is:

1. In combination with a steam generator having a plurality of tube lined walls defining a flue for the passage of flue gas and a plurality of spaced nests of tubes within said flue; an access shaft within said flue parallel to said Walls, said access shaft penetrating said nests of tubes and having a plurality of apertures therein, each said aperture being disposed in communication with a space between an adjacent pair of said nests of tubes, and means in said shaft for preventing a flow of flue gas therethrough.

'2. The combination as set forth in claim 1 wherein said access shaft consists of a continuous sheet metal pipe.

3. The combintion as set forth in claim 2 wherein said means includes a plurality of flaps movably secured in said pipe for closing each of said apertures therein in one position and for closing off said shaft to a flow of flue gas therethrough in another position.

4. The combination as set forth in claim 3 wherein said shaft is vertically disposed and each said flap is movable into a horizontal position to define an intermediate floor within said shaft.

5. The combination as set forth in claim 1 wherein said access shaft consists of a plurality of spaced pipe sections, each said section extending along the height of one of said nests of tubes and said means includes a flap in each section for closing said section to the passage of flue gas therethrough.

6. The combination as set forth in claim 1 wherein said shaft consists of a pipe suspended from one of said tube lined walls, said one wall defining a side of said access shaft.

7. The combination as set forth in claim 1 wherein said steam generator includes a flue cover over said walls and said shaft passes through said cover and includes a closeable cover for permitting entry into said shaft.

8. The combination as set forth in claim 1 wherein each of said walls includes a plurality of tubes secured together in gas tight relation.

References Cited UNITED STATES PATENTS 2,310,801 2/1943 Mayo et al 122-235 2,654,352 10/1953 Schoenfeld 122494 3,229,672 1/1966 Mirigay 122-494 XR KENNETH W. SPRAGUE, Primary Examiner.

U.S. Cl. X.R. 122494 

